Pump unit

ABSTRACT

A pump unit includes a housing which has an outwardly open recess, in which a pump is arranged. The recess is closed by a cover. The pump unit also has a pressure relief valve which is arranged in an opening of the housing which opens to the outside. The pressure relief valve has a valve seat which is formed in the opening and against which a seat valve member is loaded in the closing direction by way of a prestressed compression spring. The seat valve member can be loaded in the opening direction by the outlet pressure of the pump.

The invention relates to a pump unit having a housing which has anoutwardly open recess, in which a pump is arranged, the recess beingclosed by a cover, and having a pressure relief valve which is arrangedin an opening of the housing which opens to the outside, which pressurerelief valve has a valve seat which is formed in the opening and againstwhich a seat valve member is loaded in the closing direction by way of aprestressed compression spring, which seat valve member can be loaded inthe opening direction by the outlet pressure of the pump.

It is an object of the invention to provide a pump unit of the typementioned at the outset, which pump unit has a simpler construction withfewer components and can be assembled more simply.

According to the invention, this object is achieved by virtue of thefact that the recess and the opening, extending parallel to one anotheron a housing outer wall, open to the outside out of the housing and canbe closed by way of a common cover.

As a result of this configuration, both the recess, in which the pump issituated, and the opening for the pressure relief valve can be closed byway of the mounting of one cover.

Here, the cover is of simple construction and can be produced simply ifthe housing outer wall is planar in the region of the orifices of therecess and the opening.

It likewise leads to a reduction of the components and the assemblyoutlay if a sealing groove which encloses the orifices of the recess andthe opening jointly is formed in the housing outer wall, into whichsealing groove an elastic seal of corresponding shape is inserted,against which seal the cover is in contact sealingly in its closedposition.

In order to fasten the cover to the housing, the cover can be stressedinto contact with the housing outer wall by way of screws which can bescrewed into threaded holes in the housing.

Here, the cover can be stressed homogeneously against the housing wallif the cover can be stressed onto the housing outer wall by way of atleast two pairs of screws, the connecting lines of the two screw pairsintersecting, in particular, in the middle of the orifice of the recessof the pump.

For exact positioning of the cover and possibly for axial guidance ofthe pump which is inserted into the recess or part of the pump, thecover can have a guide attachment on its side which faces the housing,which guide attachment corresponds to the cross section of the orificeof the recess and protrudes into the recess.

If the compression spring which loads the seat valve member in theclosing direction is supported on the cover, the prestress of thecompression spring is also automatically generated by way of themounting, by the screw pairs stressing the cover against the housingwall.

In order to guide the seat valve member between the open and closedposition, the seat valve member can have a coaxial guide shank on itsside which faces away from the valve seat, which valve shank is guideddisplaceably in a guide hole which is formed in the cover.

Here, the guide shank can be configured as a locating shank and theguide hole can be configured as a locating hole for exact guidance.

In order that hydraulic fluid can flow into and out of the free volumein the guide hole behind the guide shank and the seat valve member canmove largely freely in the guide hole, the guide shank can have one ormore axial grooves on its cylindrical circumferential face in its regionwhich dips into the guide hole.

In order to simplify mounting, the locating hole can have an insertionradius on its orifice.

In a manner which saves installation space and makes it possible to usesimple standard components, the compression spring can be a compressioncoil spring which encloses the locating shank at a radial spacing and issupported with its one end on the seat valve member and with its otherend on the cover.

Here, the compression coil spring can be guided with its one end on acylindrical attachment of the seat valve member and/or with its otherend on an annular depression in the cover.

If the valve seat is a conical valve seat and the seat valve member is aconical seat valve member, this leads to reliable closing of thepressure relief valve.

Separate lines to a container for the shut-off hydraulic fluid are notrequired if the outlet side of the pressure relief valve is connected tothe inlet of the pump via a channel which is formed in the housingand/or the cover.

The pump can be a charge pump, the outlet of which is connected to theinlet of a main pump and always reliably supplies the latter withhydraulic fluid, in particular at a pressure between approximately 2 barand 10 bar above atmospheric pressure.

If the housing of the charge pump can be flange-connected to the mainpump here, a compact hydraulic unit is produced.

One exemplary embodiment of the invention is shown in the drawing andwill be described in greater detail in the following text.

In the drawing:

FIG. 1 shows a side view of a gerotor pump without a cover,

FIG. 2 shows a section along the line II-II in FIG. 1,

FIG. 3 shows a section along the line III-III in FIG. 1, and

FIG. 4 shows a section along the line IV-IV in FIG. 1.

The gerotor pump which is shown has a housing 1 which is configured as aconnecting plate and has a first housing outer wall 2, to which a mainpump which is configured, for example, as an axial piston pump can beflange-connected, the suction connector of which is supplied withhydraulic fluid at a charge pressure by the gerotor pump which isconfigured as a charge pump.

The second housing outer wall 3 of the housing 1 which is parallel tothe first housing outer wall 2 is of planar configuration.

A cup-like recess 4 of circular cross section opens to the outsidetoward said second housing outer wall 3, in which recess 4 an annularexternal rotor 5 of the gerotor pump is mounted rotatably. The annularexternal rotor 5 is provided on its radially circumferential inner wallwith internal teeth which are in meshing engagement with the externalteeth of an internal rotor 6.

Here, the number of internal teeth is greater by at least one than thenumber of external teeth.

The internal rotor 6 is arranged fixedly on a drive shaft 7 which ismounted rotatably in anti-friction bearings 8 and 9 on both sides of theinternal rotor 6 and can be driven rotatably about a rotational axis 21by a drive (not shown) via the drive shaft of the main pump.

Next to the recess 4, an opening 10 which is configured as a hole isarranged in parallel in the housing 1, which opening 10 likewise opensto the outside toward the second housing outer wall 3.

A sealing groove 11 which encloses the orifices of the recess 4 and theopening 10 jointly is formed in the second housing outer wall 3, intowhich sealing groove 11 an elastic seal 12 which is configured as asealant tape of corresponding shape is inserted. A cover 13 is incontact with the second housing outer wall 3 via the seal 12, whichcover 13 covers both the orifice of the recess 4 and the orifice of theopening 10 and has a guide attachment 14 which projects toward thehousing 1. The cross section of the guide attachment 14 corresponds tothat of the recess 4, and said guide attachment 14 protrudes into saidrecess 4 in such a way that it forms an axial guide for the externalrotor 5.

The other axial guide is formed by the bottom 15 of the cup-shapedrecess 4.

On one side of the internal rotor 6, the drive shaft 7 protrudes througha bottom-side bearing hole 16 in the housing 1, in which bearing hole 16the first anti-friction bearing 8 is arranged.

The other end of the drive shaft 7 protrudes into a bearing recess 17which is not of continuous configuration in the cover 13, in whichbearing recess 17 the second anti-friction bearing 9 is inserted, thedrive shaft 7 being guided axially by way of the bottom 18 of saidbearing recess 17.

The cover 13 can be stressed onto the second housing outer wall 3 by wayof the screw heads 20 of four screws 19 which are arranged in thecorners of a rectangle. The screws penetrate corresponding holes in theedge region of the cover 13 and holes which are aligned therewith in thehousing 1 and can be screwed with their threaded shanks into threadedholes which are formed in a housing part of the main pump.

In each case two screws 19 are arranged so as to lie diametricallyopposite one another with regard to the rotational axis 21 of the driveshaft 7.

Two screws 19 can therefore be connected in each case by an imaginaryconnecting line, the two connecting lines 22 of the two pairs crossingin the rotational axis 21 of the drive shaft 7 (tandem screwconnection).

The hole of the opening 10 merges at a spacing from the second housingouter wall 3 into a conical valve seat 23 of a pressure relief valve 32,the valve passage of which can be closed by way of a conical seat valvemember 24 which is arranged in the opening 10.

On its side which faces away from the conical valve seat 23, the conicalvalve seat member 24 has a coaxial locating shank 25 which protrudeswith its free end into a locating hole 26 of corresponding cross sectionwhich is formed in the cover 13, which locating shank is guidedcoaxially with respect to the conical valve seat 23 in said locatinghole 26.

The locating shank 25 is provided on its inner circumferential face withsix axial grooves 27 in a manner distributed uniformly over itscircumference.

The opening of the locating hole 26 is provided with an insertion radius28.

The locating shank 25 is enclosed at a radial spacing by a compressioncoil spring 29 which is supported with its one end on the cover 13 andis in contact by way of its other end with the conical seat valve member24 and loads the latter with prestress into its closed position on theconical valve seat 23.

The opening pressure, at which the conical seat valve member 24 lifts upfrom the conical valve seat 23, is determined by way of the prestress.

Counter to the force of the compression coil spring 29, the conical seatvalve member 24 is loaded in the valve opening direction by the outletpressure of the gerotor pump via a branch 30 of the outlet 31 of thegerotor pump. The outlet channel 31 of the gerotor pump at the same timeforms the inlet channel of the main pump.

If the delivery pressure of the gerotor pump rises above the openingpressure of the pressure relief valve 32, the conical seat valve member24 is lifted up from the conical valve seat 23 and hydraulic fluid canflow out via the opening 10 and a channel 33 which is formed in thehousing 1 to an inlet chamber 34 of the gerotor pump, to which inletchamber 34 a suction connector of the gerotor pump is also connected.

The channel 35 which can be seen in FIG. 3 is the outlet channel of themain pump. The outlet channel 35 and the inlet channel 31 merge intokidney-shaped grooves on the outer wall 2 of the housing 1.

1. A pump unit, comprising: a housing including an outwardly openrecess, a pump arranged in the recess, and the recess closed by a cover;and a pressure relief valve arranged in an opening of the housing, thepressure relief valve configured to open to an outside of the housing,the pressure relief valve including a valve seat formed in the opening,and the valve seat configured such that against the valve seat a seatvalve member is loaded in a closing direction by way of a prestressedcompression spring, the seat valve member configured to be loaded in anopening direction by an outlet pressure of the pump, wherein the recessand the opening extend parallel to one another on a housing outer wall,wherein the recess and the opening open to the outside out of thehousing, and wherein the recess and the opening are configured to beclosed by the cover.
 2. The pump unit as claimed in claim 1, wherein thehousing outer wall is planar in a region of orifices of the recess andthe opening.
 3. The pump unit as claimed in claim 2, further comprising:a sealing groove configured to enclose the orifices of the recess andthe opening jointly, the sealing groove formed in the housing outerwall; and an elastic seal of corresponding shape inserted into thesealing groove, wherein, in a closed position, the cover is in contactsealingly against the elastic seal.
 4. The pump unit as claimed in claim1, wherein the cover is configured to be stressed into contact with thehousing outer wall by way of screws configured to be screwed intothreaded holes in the housing.
 5. The pump unit as claimed in claim 1,wherein the cover includes a guide attachment on a side which faces thehousing, the guide attachment configured to correspond to a crosssection of the orifice of the recess and to protrude into the recess. 6.The pump unit as claimed in claim 1, wherein the compression springwhich loads the seat valve member in the closing direction is supportedon the cover.
 7. The pump unit as claimed in claim 1, wherein the seatvalve member includes a coaxial guide shank on a side which faces awayfrom the valve seat, the guide shank configured to be guideddisplaceably in a guide hole formed in the cover.
 8. The pump unit asclaimed in claim 7, wherein the guide shank has at least one axialgroove in a cylindrical circumferential face in a region which dips intothe guide hole.
 9. The pump unit as claimed in claim 6, wherein thecompression spring is a compression coil spring configured to enclosethe guide shank at a radial spacing and is supported with a first end onthe seat valve member and with a second end on the cover.
 10. The pumpunit as claimed in claim 1, wherein the valve seat is a conical valveseat and the seat valve member is a conical seat valve member.
 11. Thepump unit as claimed in claim 1, wherein an outlet side of the pressurerelief valve is connected to an inlet of the pump via a channel formedin at least one of the housing and the cover.
 12. The pump unit asclaimed in claim 1, wherein the pump is a charge pump, and an outlet ofthe charge pump is connected to an inlet of a main pump.
 13. The pumpunit as claimed in claim 12, wherein the housing of the charge pump isconfigured to be flange-connected to the main pump.